High heat resistant nylon can be obtained by polycondensation of aromatic dicarboxylic acids or aromatic diamines. High heat resistant nylon may have a semi-aromatic structure and a semi-crystalline structure, and may be used in various fields requiring high heat resistance due to its significantly higher heat resistance as compared to general nylon.
Examples of typical high heat resistant nylon include PA4T, PA6T, PA9T, PA10T, PA11T, PA12T, and the like. High heat resistant nylon using C9 or longer chain diamines may directly employ a homopolymer, or may employ a copolymerized polymer using a comonomer (dicarboxylic acid or diamine).
Generally, PA4T and PA6T cannot be processed due to an extremely high melting point of the homopolymer. Melt processability thereof can be improved by introduction of a large amount of (tens of %) comonomers. For PA6T, adipic acid, isophthalic acid or the like is widely used as a comonomer, and short-chain or long-chain aliphatic diamine, alicyclic diamine, branched chain aliphatic diamine, short-chain or long-chain aliphatic dicarboxylic acid, alicyclic dicarboxylic acid, branched chain aliphatic dicarboxylic acid, and the like may be used.
In high heat resistant nylon products for LED reflectors which require excellent optical properties and discoloration resistance, alicyclic dicarboxylic acid may be used instead of aromatic dicarboxylic acid in order to produce products exhibiting excellent optical/thermal properties, or a monomer capable of increasing a glass transition temperature (Tg) may be copolymerized in order to prevent deterioration of properties of nylon products at high temperature. However, such copolymerization cannot prevent nylon from suffering inherent discoloration when exposed to air at high temperature.
Due to such drawbacks, in products requiring discoloration resistance, high heat resistant polyester products may be used instead of high heat resistant nylon. However, high heat resistant polyester products generally exhibit inferior heat resistance as compared to high heat resistant nylon, and have drawbacks of poor hydrolyzability and moldability under humid conditions despite excellent discoloration resistance.
Thus, there is a need for a novel polyamide ester resin (amide-ester hybrid resin), which exhibits superior properties as compared to existing high heat resistant nylon products in terms of heat resistance, discoloration resistance and the like, and which have improved moldability.